This problem is caused because Ubuntu is not a supported platform and Oneric has made some substantial changes to how shared libraries must be linked, and this change is not backward compatible with other distributions such as RedHat and its derivatives. Although not recommended, you should be able to fix this by adding the linker option --no-as-needed. To do this with buildclient, you would use a command like:

buildclient -o simpcl -f "-Xlinker --no-as-needed simpcl.c"

and this should get you past your linker error. You should also be able to add this to the CFLAGS environment variable.